DNA endoreplication level in endosperm and in cotyledons during seed development in three dicotyledonous species

The DNA content of nuclear and cellular endosperm and in cotyledons in the course of seed development in Helianthus annuus, Pisum sativum and Vicia faba was cytophotometrically measured after Faulgen's reaction. Helianthus annuus is characterized by the lowest endoreplication dynamics attaining a maximum DNA content of 48C in nuclear endosperm, which corresponds to four endoreplication rounds, and 16C DNA (three rounds) in cotyledons. In Pisum sativum cellular endosperm in the studied stages of seed development was absent and the highest DNA content in cotyledons was 512C DNA; this corresponds to eight endoreplication rounds. In Vicia faba, the maximum DNA endoreplication level was 1536C in nuclear endosperm, which corresponds to nine endoreplication rounds; in cotyledons the maximum DNA content was 64C (five rounds). In the course of seed development, differences in the dynamics of DNA endoreplication in throphic tissues of the examined species seem to be similar to differences in the endoreplication level in root and leaf parenchyma, but the DNA endoreplication level is much higher in throphic tissues. Therefore, the endoreplication pattern might be species-specific and genetically conditioned.